The present invention relates to image forming equipment of the type performing a predetermined image forming operation by use of a stepwise drive source such as a stepping motor or pulse motor.
Today, a copier, facsimile transceiver, printer or similar image forming equipment implemented with an electrophotographic procedure or an electrostatic recording procedure is extensively used. This kind of equipment usually has a stepping motor or pulse motor or similar stepwise drive source for transporting a recording medium or moving either one of scanning optics and a document, as disclosed in Japanese Patent Laid-Open Publication No. 179477/1986 by way of example. It has been customary to provide such equipment with a sensor for determining whether or not a member to be driven stepwise such as a recording medium has reached a predetermined position at least upstream of a position where an image forming operation is to begin with respect to the direction of movement of the member of interest. The above-mentioned predetermined position is used as a reference.
In the stepwise drive described above, a step made up of a drive state wherein the recording medium, for example, is in movement and a stop state wherein it is in a halt is repeated. At least in the drive state, it is impossible to forcibly and immediately stop the movement of the recording medium, i.e., the movement is controlled only on a step basis. This brings about a drawback that when the recording medium is moved with the above-mentioned predetermined position used as a reference, an error corresponding to the displacement caused by one step at maximum occurs at the start of the image forming operation. While the displacement per step may be reduced to reduce such an error, a decrease in the displacement directly translates into an increase in the period of time necessary for the image forming operation to be completed.